HIV causes AIDS by killing or interfering with the normal functioning of T-helper cells.An infected person may have 200 T helper cells per mm3 of blood compared to 800 - 1200 cells per mm3 for an uninfected person.Without sufficient numbers of T helper cells the immune system cannot adequately stimulate B cells to produce antibodies or cytotoxic T cells to destroy infected cells.Memory cells may also become infected and destroyed.As infected individuals cannot produce an immune response they are susceptible to infections and cancer. Opportunistic secondary infections lead to weight loss and diarrhoea and eventually cell death. HIV does not kill directly but leaves individuals susceptible to other diseases and unable to mount a successful immune response.
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Specification: AQA Biology (7401), AS-level, 3.2.4 Cell recognition and the immune system. Topic: Cell Recognition and the Immune System.
Key terms in this lesson
- antibody
- A Y-shaped protein, made of four polypeptide chains with variable regions complementary to a specific antigen, produced by B plasma cells.
- B-lymphocyte
- A type of white blood cell, matured in the bone marrow, responsible for the humoral immune response and antibody production.
- T-lymphocyte
- A type of white blood cell, matured in the thymus gland, responsible for the cell-mediated immune response.
- memory cell
- A long-lived lymphocyte, produced during the primary immune response, that allows a faster secondary immune response on re-exposure to the same antigen.
More in Cell Recognition and the Immune System
- Herd Immunity
- Vaccination Programme Failure
- Ethics
- MMR Vaccine Case Study
- Structure of HIV Virus
- Replication of HIV Virus
- The ELISA Test
- Antibiotics
All 30 lessons in Cell Recognition and the Immune System · All AQA AS-level Biology topics